The present invention relates generally to automated distribution systems for storing and retrieving goods. More particularly, the invention relates to a rotatable storage carousel and supporting mechanisms for inserting and removing variable-sized cartons from the carousel while it remains in continuous motion. As used in the present specification and claims, the terms "carton" and "cartons" include cartons, boxes, bins, totes and other containers for storing or holding items.
Many modern production and warehousing facilities require the storage and retrieval of thousands of inventoried items. The goods may be stored in cartons due to their size or delicate construction. Therefore, storage requires loading the containers and delivering them to a known location where they can later be retrieved as necessary. When an order is received, the desired items must be retrieved from their respective positions and kitted, prepared for shipping, or otherwise put to use. An efficient storage operation requires the ability to both store and retrieve a wide variety of goods and to rapidly and effectively dispose of the retrieved items. A wide variety of warehousing/distribution systems have been proposed to reduce the labor required in warehousing operations. However, few systems have addressed both the storage and production requirements for a global distribution solution.
Certain storage and retrieval systems use large multi-level fixed storage shelves in combination with an extractor or picking mechanism that must travel to a particular shelf to pick the desired inventory item. For example, a mobile unit may traverse along a series of stationary vertical racks. The mobile unit is equipped with mechanisms for loading and unloading the vertically based storage racks. Such systems have several drawbacks. Initially, they are limited to a small number of insertion or extraction transactions each time the extractor is operated due to the need to move the picking mechanism after each insertion or extraction operation. Additionally, such systems traditionally have fixed locations for storing each type of goods received within the warehouse. This prevents efficient space utilization since the fixed location occupies the same amount of space regardless of whether a particular inventoried item has two stock units or 2000. Therefore, such systems are extremely wasteful of valuable building space.
Storage structures have also been proposed that include a movable multi-tiered storage carousel having a large number of arrays of vertically-spaced container racks arranged to form a continuous horizontally operating rack assembly which travels about a track. However, such systems have numerous drawbacks which limit their feasibility in high volume operations. Most notably, in order to insert a container onto, or extract a container from a rack on the storage carousel, the carousel must be stopped adjacent to the insertion and extraction mechanism and the container disengaged or inserted. The time required to start and stop the carousel inherently limits the speed at which container insertion and extraction operations may occur. Additionally, the requirement of repeatedly starting and stopping a carousel which may carry on the order of 700,000 tons of material, can be extremely taxing in terms of both power requirements, component wear and drive motor life. Further, it is difficult to stop such a massive structure with enough control to precisely position the containers for either insertion or extraction.
An improved automated storage and retrieval system having a storage carousel that may remain in continuous motion while containers are inserted onto or extracted from the carousel storage racks has also been developed. This system may be designated the rotating storage structure unit (RSSU).
The automated storage carousel of the RSSU dispenses with the need for stopping and starting the rack assembly for loading and unloading containers from the storage racks. This system is able to store and retrieve inventoried items in great quantities and varieties. This storage system may incorporate a relatively simple hanger arrangement for holding containers stored thereon. The system is the subject of several U.S. patents, including the following: U.S. Pat. No. 5,556,247; U.S. Pat. No. 5,282,712; U.S. Pat. No. 5,090,863; and U.S. Pat. No. 4,983,091. These patents are assigned to the assignee of the subject application and are incorporated herein by reference.
There is also a need for a smaller and less complex, and thus, less expensive, version of the RSSU. Such a small-scale system should provide rapid storage or staging and retrieval of cartons. The carton size and weight may be limited, although it need not be, to that which can be manipulated manually. This small-scale system should have a high transaction rate, which is the speed at which carton insertion and extraction operations occur. It should also be capable of installation, for instance, in an existing warehousing facility with minimal impact on other facility resources, such as sources of electrical power and compressed air. Such a system should automatically receive, store and retrieve individual cartons at a rate exceeding ten cartons per minute.